NEW BRITAIN - Findings from a city-funded environmental report examining a proposed Tilcon quarry expansion in Plainville concluded the project would nearly double the city’s water supply in 40 to 45 years.

The study was required by law as part of a proposal that would allow Tilcon to mine 131 acres of protected watershed owned by the New Britain Water Company.

According to the executive summary of the 500-plus page report, the mining would leave a reservoir that would increase the city’s water supply by 45 percent.

Tilcon and the city originally estimated in 2016 that the new reservoir created by the project could provide 160,000 gallons a day of drinking water. But the report released by the state Council on Environmental Quality Wednesday morning said the new reservoir could safely provide 2 million gallons a day of drinking water, according to Lenard Engineering. The firm was hired by the city in 2007 and 2016 to do an environmental impact study of the project. A similar quarry proposal was dropped in 2008 under stiff public opposition.

The study released Wednesday also indicated that the quality of the water in the new reservoir created by 40 years of mining wouldn’t have “significant differences” from the water in the city’s existing reservoirs. The tests were based on “samples assumed to be representative of the proposed reservoir,” the report said.

The report also indicated that “no impacts to the existing air quality permits or potential emissions are anticipated as a result of the quarry expansion.”

Under the proposal, Tilcon would mine New Britain-owned protected watershed land in Plainville for 40 to 50 years before returning the land to the city as a reservoir. Tilcon would lease the land from the city for an unspecified amount during the mining and give nearly 300 acres of open space to Plainville, New Britain and Southington as part of the deal. In a 2007 proposal Tilcon offered the city of New Britain $15 million to lease the mineral rights to the property. The city has said that no financial terms have been discussed.

The legislature must vote to approve a change of use for the land in order for Tilcon to mine the property. The state Department of Health must also sign off on the plan.

A law passed in 2016 carefully delineated the steps the city must take to get the project on the legislative agenda including hiring a consultant to do an environmental study of the area.

The state’s Water Planning Council and the Council of Environmental Quality will have 90 days to review the report and submit comments to the city.

The city will have 60 days to hold a public hearing on the findings of the study.

City officials and Tilcon representatives said Wednesday they had not yet seen the report.

“While Tilcon has not received the report, we understand that Lenard Engineering has released its study on a proposed change of use of watershed lands in Plainville owned by the City of New Britain,” said a statement from Tilcon. “When we receive the report, we will spend the time necessary to learn more about the study’s results and findings. As appropriate, the company will also participate in the review process established by the legislature.”

The proposal has generated spirited opposition from area residents and environmentalists who fear that the change in land use will imperil protected watersheds throughout the state. Protect Our Watersheds CT, a group formed after the 2016 proposal came to light, has at least 2,500 signatures on a petition asking the legislature to quash the plan.

Attorney Paul Zagorsky, one of the founders of the group, asked the Council of Environmental Quality Wednesday morning to consider going to the watershed site before they form their written recommendations to the city and the state.

“You’ll see what’s at stake here and what’s going to happen,” said Zagorsky, who handed out photos of the flora and fauna that can be found in the watershed which acts as a tributary to Shuttle Meadow Reservoir.

Gary Wall, president of Tilcon, told The Press in November 2016 that his company has another 25 years of mining left in the current location off Woodford Avenue in Plainville. The proposal would extend the quarry toward Bradley Mountain in Southington.

Plainville town officials said Wednesday that the mining operation off Woodford Avenue was reaching its boundaries, but still has more than a dozen years of quarrying left. Tilcon also owns more than 175 acres of land in a quarry off North Mountain Road that has seen minimal mining throughout the years, according to a July 2017 town Planning and Zoning Commission report.

The company’s main quarrying operation on Woodford Avenue includes large processing equipment, said Plainville Town Planner Mark DeVoe. The company would either have to transport the rock from the North Mountain Road quarry to Woodford Avenue for processing or move the equipment to effectively mine the 175-acre property, DeVoe said. “It’s a considerable amount of expense.”

Lisa Backus can be reached at 860-801-5066 or Lbackus@centralctcommunications.com.